1. Field of the Invention
Fatty acids contained in co-product streams, waste or recycled fatty acid stock such as soap stock can be converted into fatty acid (C1-5) alkyl esters using an acidic resin.
2. Related Art
Fatty acid alkyl esters, such as methyl esters, find use as chemical intermediates and fuels. Fatty acid methyl esters of vegetable oil are commonly referred to as Biodiesel. Renewable resource chemicals are important as they are sustainable in contrast to those derived from fossil fuels.
Currently, Biodiesel and other fatty acid alkyl esters are often produced from refined triglyceride feedstocks via base catalyzed transesterification. When glyceride oils, e.g., animal fats or vegetable oils, are refined to remove free fatty acids and other impurities by alkali refining, the aqueous alkaline solution which is separated from the bulk of the refined oil contains alkali soaps of fatty acids together with substantial quantities of free fatty acids, glycerides thereof, and various impurities including water-soluble phosphatides such as lecithin. Some of the free fatty acids, glycerides, and impurities ordinarily will be emulsified in the resulting aqueous mixture by the soaps and the phosphatide-type components. This aqueous mixture is commonly known as “soap stock”.
Alternate, less refined or recycled fatty acid feedstocks are available. These feedstocks include acidulated soap stock (acid oils), gums (phospholipid enriched by-product stream obtained in edible oil refining), used grease from restaurants, and all other acylglyceride esters of fatty acids that contain high levels of free fatty acids (FFA).